How to Convert GPT to MBR or Convert MBR to GPT without Losing Data?

March 20, 2019

This paper gives a brief introduction of MBR and GPT and tells you how to make conversion between GPT and MBR disk without data loss via AOMEI Partition Assistant.

Contents:

About MBR and GPT

WWhen need to convert MBR/GPT disk?

How to convert between MBR and GPT without losing data?

How to convert GPT to MBR or convert MBR to GPT without operating system?

About MBR and GPT Disk

You may find that sometimes you need to convert MBR to GPT disk, but sometimes, you need to convert GPT to MBR disk. Why? Here we will introduce you about MBR and GPT disk first.  

MBR - Master Boot Record: it is a guide sector in the very front of drive. It was named in 1983 when partitioning the hard disk or flash disk of IBM compatible personal computer. At that time, PC DOS 2.0 was able to support hard disk. MBR describes the information of logical, including file system and organization type. Besides, MBR also contains the executable code produced when computer loads operating system in the second stage of start or the boot record connecting every partition (VBR). Such MBR is usually called boot routine.

Note: MBR cannot exist in a media which cannot be partitioned, such as soft disk.

GPT - GUID (Globally Unique Identifiers) Partition Table: it is a new standard of disk partition table originating from EFI (Extensive Firmware Interface). Compared with MBR, it provides a more flexible disk partition principle.

What are the limitations of MBR disk?

  1. MBR disks only support up to 2TB partition size and support four primary partitions only. If partition size surpasses 2TB, the rest space will show as unallocated space.

  2. If more partitions are needed, you have to build a secondary structure known as extended partition, and then you can create logical partitions. 

  3. MBR partitioning rules are complex and poorly specified.

What are the advantages of GPT disk?

  1. It can make full use of a very large size to break the 2TB limit of MBR disks.

  2. GPT disks allow an almost unlimited number of partitions. Though Windows implementation restricts the number to 128, it is completely sufficient for using.

  3. Each GPT partition has a unique identification GUID and a partition content type. And you can have more primary partitions.

  4. There nearly isn’t any limitation to the size of partition. The sector is numbered by a 64-bit integer. A partition with such number of sectors, can it be small?

  5. Partition on GPT disk has self-contained backup which is stored on the end of the disk while the original one is saved on the start. When one of the two is destroyed, you can restore it with the other.

  6. Every partition on GPT disk can have a name which is different from partition label.

When Need to Convert MBR/GPT Disk?

As for the differences between MBR disk and GPT disk, you may need to convert GPT to MBR disk, or convert MBR to GPT disk for better usage.

1. Convert MBR to GPT for full using

As mentioned above, MBR disks only support up to 2TB partition size, so if you have a disk which is MBR formatted and larger than 2TB, you could only use 2TB disk size among it, but the reset of it could not be used. Or when you need to create more than four primary partitions, converting MBR disk to GPT disk is necessary to make full use of the disk space.

2. Convert GPT to MBR for system compatibility

On the other hand, since Windows 95/98/ME, Windows NT4, Windows 2000, Windows 2003 32-bit, or Windows XP 32-bit version does not support GPT partitions, a GPT disk will display as GPT protective partition in these systems, thus you could not access the data until you convert it back to MBR disk. In such situation, you have nothing to do but to convert GPT to MBR disk. 

Note:

If you want to convert any larger than 2TB GPT disk back to MBR disk, you'd better ensure that the data does not account for space more than 2TB. Otherwise, the overloaded data will get lost. However, if you really want to convert your GPT drive on which there are more than 2TB data into MBR disk, you can transfer the extra data to other place via a data migration software before converting.

3. Windows cannot be installed to this disk error

Sometimes you may meet an error message “Windows cannot be installed to this disk. The select disk is of GPT partition style”. To fix this error, you need to convert GPT to MBR before installing system. While in other situations, you may get the error: “Windows cannot be installed to this disk. The select disk is of MBR partition style”. For this circumstance, you need to convert MBR to GPT partition style.

How to convert MBR to GPT or convert GPT to MBR without losing data?

First, To convert GPT to MBR or MBR to disk without data loss, you can apply AOMEI Partition Assistant Professional. Let’s see how it works.

Free download AOMEI Partition Assistant Professional to have a try. Windows 10/8/7 is supported. If you are working with Windows Server 2003, 2008, 2012, 2016, 2019, you can apply AOMEI Partition Assistant Server edition.  

Step 1.  Install and launch AOMEI Partition Assistant Professional. Select the data disk you want to convert and right click it, and then select "Convert to GPT Disk" (or Convert to MBR Disk) in the drop-down menu.

Convert Data Disk to GPT

Step 2. Click "OK" after confirming the operation.

OK to GPT Data Disk

Step 3. You can preview the conversion. To save the change, please click "Apply" on the toolbar and wait for process to complete.

Apply to GPT Data Disk

AOMEI Partition Assistant Professional also allows you to convert system disk between MBR disk and GPT disk without losing data. But you need to know:

1. AOMEI Partition Assistant will converting system disk between MBR and GPT partition style without losing data. But in case of some unexpected accidents which may cause data loss, you need to backup system before converting.

2. Converting system disk from MBR to GPT needs your computer’s motherboard supports EFI/UEFI boot mode. And after converting, you need to change boot mode from Legacy BIOS to UEFI, otherwise, your PC won’t boot successfully.

3. Similarly, converting system disk from GPT to MBR needs you change boot mode from UEFI to Legacy BIOS.

How to convert GPT to MBR without operating system?

When installing Windows 10/8/7, you may get an error saying that Windows cannot be installed to this disk: The selected disk is of MBR partition style or GPT partition style. In that case, you need to convert disk from MBR to GPT or from GPT to MBR before installing Windows. AOMEI Partition Assistant can also help you - You can use AOMEI Partition Assistant to create a bootable media to boot the computer, and then, use it to convert MBR to GPT or convert GPT to MBR without data loss. Refer to the steps listed below:

Step 1. Insert an USB flash drive or CD to another working computer running Windows 10/8/7, and launch AOMEI Partition Assistant.

Step 2. Click on "Make Bootable Media "and follow the wizard to finish creating a bootable media.

Make Bootable Media

Step 3. Insert this bootable disk to the computer that you’re having problem installing Windows on, and then boot it from this bootable media. You may need to change boot order to boot from this bootable USB drive.

Step 4. When the interface of AOMEI Partition Assistant is loaded, you can convert MBR to GPT or convert GPT to MBR according to your needs as the same way we demonstrate above. 

After that, you should be able to install Windows on this disk.

Notes:

  • For conversion between MBR and GPT disks on Laptop, please make sure the power supply is sufficient.

  • To ensure the data is consistent, do not abnormally terminate the program during the conversion process.